Aqueous chemical solutions are used in a variety of situations. For example, in different applications, aqueous cleaning solutions are used to clean, sanitize, and/or disinfect kitchens, bathrooms, schools, hospitals, factories, and other similar facilities. Aqueous cleaning solutions include one or more chemical species dissolved in water. The chemical species impart various functional properties to the water such as cleaning properties, antimicrobial activity, and the like. In different applications, an aqueous cleaning solution may be supplied by a manufacturer in a dilute, ready-to-use form or as a concentrate that is diluted onsite to form a working solution. Supplying a concentrate has the advantages of reducing shipping costs and minimizing the amount of onsite storage required to hold the chemical before use.
One way to supply concentrated chemical for onsite dilution is to provide solid chemical concentrate that is dissolved in an onsite dispenser to produce a comparatively dilute working solution. For example, a chemical can be provided as a powdered, flaked, or granular solid that is dissolved onsite in a dispenser. Another form of solid concentrate is a “cast” or block solid that is typically cast within a mold or container. The block solid can be dissolved by spraying a solvent on the block, thereby dissolving the exposed surface of the block to form a working solution. The working solution falls into a reservoir or is directed by a conduit to a cleaning apparatus. When the chemical compound is completely utilized, a fresh solid block can be inserted into the dispenser to recharge the dispenser for continued operation.
While a solid block chemical concentrate can be convenient to transport, store, and use, it can be challenging to control the concentration of the chemical in the working solution formed by applying solvent to the solid block. The rate at which the solid block erodes can change based on factors such as the temperature of the solvent, the length of time the solvent is applied to the block, the volume of solvent applied to the block, and similar factors. For example, the solid block may dissolve slowly upon being first wetted with solvent and dissolve more rapidly as solvent is continuously applied to the block. As a result, the collected solution produced during a dispense event can have a chemical concentration that is an average of the different chemical concentrations released during the dispense event. When an operator generates a comparatively large volume of working solution, the variability in the chemical concentration during the dispense event may be averaged away and negligible. However, when an operator seeks to generate a comparatively small volume of working solution, such as an amount to fill a handheld spray bottle, the variability in the chemical concentration may be more impactful.